In individual patients the natural resorption of CSF is blocked or reduced because of malformation or following bleeding or infection. If the missing natural resorption is not compensated for the patient will develop hydrocephalus (increased intracranial pressure with brain damage). To avoid this the patient usually needs a lifelong drainage of CSF to the venous system or the abdomen.
When the infusion of fluid in the venous system is long-lasting as when shunting hydrocephalus there is an increased risk of thrombosis or infection caused by the foreign material of the catheter. Thrombosis lead to stop in the blood flow and infection makes it necessary to remove the catheter and treat with antibiotics before putting in a new catheter. The problem with thrombosis is reduced by letting the fluid conducting catheter end in the right atrium of the heart where the fast blood flow reduces the risk of thrombosis, but the risk for infection is still the same.
In the end of the 50's, when useful materials for catheters and pressure regulating valves became available, the most common method became draining CSF to the heart. When draining to the heart the catheter runs from the ventricular system of the brain under the skin and via a pressure or flow regulating valve that prevents backflow and further down under the skin into the deep neck vein and into the right atrium of the heart. Trials have been done where the catheter has been connected to a narrow branch of the neck vein in the hope that the fluid from the brain would prevent contact between the catheter and the blood. However, this did not function well.
To be able to regulate the blood flow from the brain and the pressure in the brain the veins in the neck are soft and have a variable volume. This results in back flow of blood, thrombosis and stop of the flow when the catheter ends in the blood in such a vein.
Today the usual method is draining to the abdomen. This removes the risk of thrombosis and is of great advantage when shunting children, as a long catheter in the abdomen can compensate for growth. In adult patients, draining to the abdomen has an important disadvantage with overdrainage and siphon effect caused by the increased pressure gradient in upright position compared with lying down. This problem is not fully solved by using antsiphon valves or other types of pressure and flow regulating valves. Another disadvantage in shunting to the abdomen is that abdominal disease, especially infection, may hinder the use of the shunt.
Obviously there exists a need to improve the methods now in use for shunting hydrocephalus. The ideal method would be to drain CSF to the sagittal sinus, the stiff vein in the middle inside the skull bone, and trials with this are in progress. However, with the conventional shunt systems of today it should be easier and less risky to find a way to drain to the deep neck vein and from there to the heart, but then without contact between the blood and any foreign material. In this way a catheter in the heart would be avoided as well as the use of X-ray, ECG or other means for this positioning.
Prior art includes a number of patent documents. U.S. Pat. No. 3,894,541 (El-Shafei et al.) discloses a method of treating hydrocephaulus preventing the contact between a shunting catheter and the circulating blood by inserting a venous end of a venous catheter into the proximal segment of the ligated neck vein against the direction of blood flow. U.S. Pat. No. 3,738,365 (Schulte) discloses an extensible catheter comprising a flexible metallic helical spring and slidable conduit sections. U.S. Pat. No. 3,769,982 (Schulte) discloses a physiological drainage system with closure means responsive to downstream suction comprising a flexible diaphragm extending across a control cavity.